Write a function called get_avg().

Given a dictionary and a key, get_avg() returns the average of all the elements in the list located at the given key.

Notes:

• If the list at the given key is empty, it should return 0.
• If the property at the given key is not a list, it should return 0.
• If the key doesn't exist within the dictionary, it should return 0.

obj = {'key': [1, 2, 3]}

output = get_avg(obj, 'key')

print(output) # --> 2